Multi-liquid type clear coating composition, multilayer coating film and method for forming multilayer coating film

Abstract

To provide a multi-liquid type clear coating composition which has excellent color reversion resistance, and normal temperature dryness and long pot life.SOLUTION: A multi-liquid type clear coating composition contains a main agent containing a polyaspartic acid ester (A1) and a prepolymer of a polyaspartic acid ester (A2), and a curing agent containing a polyisocyanate compound (B1), wherein (A2) is a reactant obtained by reacting a first polyaspartic acid ester (A21) and a second polyaspartic acid ester (A22) with an isocyanate compound (A23) so that a ratio (m1:m2) of the number m1 of moles of (A21) to the number m2 of moles of (A22) is 1:1 to 4:1, (A21) has dialkyl ester (A21a) of a first dicarboxylic acid having 4 carbon atoms, and two or more primary amino groups bonded to an alicyclic structure, in the alicyclic structure, at least one carbon atom adjacent to carbon atoms to which each of the two or more primary amino groups is bonded is a reactant with first polyamine (A21b) having a hydrocarbon group as a substituent, and (A22) is a reactant of dialkyl ester (A22a) of a second dicarboxylic acid having 4 carbon atoms with second polyamine (A22b) having two or more primary amino groups no aromatic ring, other than (A21).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a multi-liquid clear coating composition, a multi-layer coating film, and a method for forming a multi-layer coating film. [Background technology]

[0002] Patent Document 1 discloses a clear coating composition containing an acrylic polyol, a polyester polyol, a cellulose derivative, and a polyisocyanate compound. Patent Document 2 discloses a coating composition containing an aspartic acid ester and a polyisocyanate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-074720 A [Patent Document 2] Patent Publication No. 2022-66853 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a multi-liquid type clear coating composition which has excellent resistance to color reversion, as well as room temperature drying properties and a long pot life. [Means for solving the problem]

[0005] The present invention provides the following aspects [1] to [8]. [1] A base material including a polyaspartic acid ester (A1) and a prepolymer of the polyaspartic acid ester (A2); A curing agent containing a polyisocyanate compound (B1), The prepolymer (A2) is a reaction product obtained by reacting a first polyaspartic acid ester (A21) and a second polyaspartic acid ester (A22) with a difunctional or trifunctional isocyanate compound (A23) such that the ratio (m1:m2) of the number of moles m1 of the first polyaspartic acid ester (A21) to the number of moles m2 of the second polyaspartic acid ester (A22) is 1:1 to 4:1; The first polyaspartic acid ester (A21) is a dialkyl ester of a first dicarboxylic acid having four carbon atoms (A21a); a first polyamine (A21b) having two or more primary amino groups bonded to an alicyclic structure, in which at least one of the carbon atoms adjacent to the carbon atoms to which each of the two or more primary amino groups is bonded has a hydrocarbon group as a substituent; The second polyaspartic acid ester (A22) is a dialkyl ester of a second dicarboxylic acid having four carbon atoms (A22a); and a second polyamine (A22b) other than the first polyamine (A21b), which has two or more primary amino groups and has no aromatic ring, said second polyamine (A22b) being a reaction product thereof. [2] The dialkyl ester of the first dicarboxylic acid (A21a) and the dialkyl ester of the second dicarboxylic acid (A22a) are each independently represented by the following general formula (I): [ka] (In the formula, R 1 and R 2 each independently represents a chain aliphatic hydrocarbon group having 1 to 20 carbon atoms.) The multi-component clear coating composition according to the above [1], [3] The first polyamine (A21b) is represented by the following general formula (II): [ka] (In the formula, Ra1 , R a2 and R a3 each independently represents an aliphatic hydrocarbon group having 1 to 3 carbon atoms, α is the carbon atom to which the primary amino group is attached, and C β is C α ) The multi-component clear coating composition according to the above [1] or [2], [4] The second polyamine (A22b) has the following general formula (III): [ka] (In the formula, R a4 represents an aliphatic hydrocarbon group having 1 to 3 carbon atoms, C α is the carbon atom to which the primary amino group is attached, and C β is C α ) The multi-component clear coating composition according to the above [1] or [2], [5] The multi-component clear coating composition according to the above [1] or [2], wherein the prepolymer (A2) has a molecular weight of 1,000 or more and 100,000 or less. [6] The multi-component clear coating composition according to the above [1] or [2], wherein the first polyaspartic acid ester (A21) and the second polyaspartic acid ester (A22) each have an amine equivalent of 180 mgKOH / g or more and 210 mgKOH / g or less. [7] The multi-component clear coating composition according to the above [1] or [2], wherein the proportion of the prepolymer (A2) in the solid content of the main component is 4 mass % or more and 50 mass % or less. [8] the bifunctional isocyanate compound (A23) is at least one of 1,6-hexamethylene diisocyanate and isophorone diisocyanate, The multi-component clear coating composition according to the above item [1] or [2], wherein the trifunctional isocyanate compound (A23) is at least one of a nurate, a biuret and an adduct of 1,6-hexamethylene diisocyanate. [9] A colored base coating film disposed on an object to be coated; A multi-layer coating film comprising: a clear coating film disposed on the colored base coating film and formed from the multi-component clear coating composition described in [1] or [2] above.

[10] Applying a colored base coating composition onto an object to form a colored base coating film; A method for forming a multi-layer coating film, comprising: applying the multi-component clear coating composition described in [1] or [2] above onto the colored base coating film to form a clear coating film. Effect of the Invention

[0006] According to the present invention, there is provided a multi-liquid type clear coating composition which has excellent resistance to color reversion, as well as room temperature drying properties and a long pot life. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] A clear paint containing an aspartic acid ester may be mixed with a coating film (e.g., a colored base coating film or a metallic base coating film) in the lower layer, causing color reversion. Color reversion refers to a phenomenon in which the components contained in the clear paint penetrate into the lower layer and mix with each other, resulting in a decrease in design. For example, when the lower layer has a pigment, the components of the clear paint penetrate into the lower layer and the pigment in the lower layer rises up into the clear paint. As a result, the color appears to be bleeding, and the desired hue cannot be obtained. Such color bleeding is an example of color reversion. Having resistance to color reversion can be said to be a performance in which the design that can be exhibited by the coating film in the lower layer of the clear coating film is not impaired by the clear coating composition.

[0008] Aspartic acid esters generally have a small molecular weight, and clear paints containing them have a low viscosity. The low viscosity of clear paints is thought to be one of the causes of color reversion. If part of the aspartic acid ester is prepolymerized, the molecular weight increases, and the viscosity of the clear paint can be increased. However, prepolymerization shortens the pot life.

[0009] In automotive repair painting, when polishing (glossing the paint film) is performed after painting, high room temperature drying properties are required. Room temperature drying properties and extended pot life are usually trade-offs. Room temperature means 15°C to 25°C. Room temperature drying properties can also be a cause of color reversal. The higher the room temperature drying properties, the easier it is to prevent color reversal.

[0010] In the present disclosure, the reaction rate is controlled by using a prepolymer using two different aspartic acid esters, and the color reversion resistance is improved while achieving both room temperature drying property and extended pot life. The clear coating composition according to the present disclosure is particularly suitable for automobile repair.

[0011] The room temperature drying property can be evaluated using a test plate prepared by spraying a clear coating composition onto a colored base coating film formed by the method described below, and curing the test plate for 60 minutes under conditions of 23°C and 50% RH. A finger touch evaluation is performed on the test plate. If no finger marks are left on the coating film when the test plate is lightly touched, the test plate can be evaluated as having room temperature drying property. The room temperature drying property allows polishing work to be done by simply drying the test plate at room temperature for 1 hour after painting.

[0012] The pot life can be evaluated using a viscosity cup NK-2 manufactured by Anest Iwata Corporation. Specifically, it is evaluated according to the following procedure. First, the base resin, the curing agent, and the diluting component (organic solvent) are each placed at 20°C to keep the liquid temperature constant. Then, a multi-liquid clear coating composition is prepared by mixing each liquid in a predetermined amount in order. Immediately, a viscosity cup NK-2 manufactured by Anest Iwata Corporation is immersed in the multi-liquid clear coating composition and pulled out. The time from the moment of pulling out until all the multi-liquid clear coating composition is discharged is measured, and the initial value T0 Next, after the multi-liquid clear coating composition is prepared and left to stand for 45 minutes, the time (T (seconds)) from when it is pulled up to when it is discharged is measured in the same manner as above. 0 When (seconds) is within 5 seconds, the clear coating composition can be evaluated as having a long pot life.

[0013] Hereinafter, the term "hydrocarbon group" refers to a group containing carbon and hydrogen, which is a group obtained by removing one hydrogen atom from a hydrocarbon. Examples of such a hydrocarbon group include an aliphatic hydrocarbon group and an aromatic hydrocarbon group. The hydrocarbon group may be substituted with one or more substituents. The substituents are not particularly limited, but may include, for example, halogen atoms. The hydrocarbon group may have one or more N, O, S, Si, amide, sulfonyl, siloxane, carbonyl, carbonyloxy, etc. at its terminal or in the molecular chain.

[0014] Unless otherwise specified, the "aliphatic hydrocarbon group" may be linear, branched, or cyclic, and may contain one or more ring structures. Unless otherwise specified, the aliphatic hydrocarbon group may be saturated or unsaturated.

[0015] [Multi-liquid clear coating composition] The multi-liquid clear coating composition is a mixture of a base agent and a curing agent. The multi-liquid clear coating composition may be a two-liquid type. The multi-liquid clear coating composition may further include a third agent containing other components.

[0016] The base agent contains a polyaspartic acid ester (A1) and a prepolymer of the polyaspartic acid ester (A2). The curing agent contains a polyisocyanate compound (B1). By mixing the base agent and the curing agent, a curing reaction occurs to obtain a cured coating film.

[0017] <Main ingredient> The base material contains a polyaspartic acid ester (A1) and a prepolymer of the polyaspartic acid ester (A2). The solid content concentration of the base material is, for example, 30% by mass or more and 80% by mass or less.

[0018] Prepolymer (A2) The prepolymer (A2) is a reaction product of a first polyaspartic acid ester (A21), a second polyaspartic acid ester (A22), and a difunctional or trifunctional isocyanate compound (A23).

[0019] The prepolymer (A2) made from the polyaspartic acid ester has excellent compatibility with the polyaspartic acid ester (A1) contained in the base resin, so a clear coating film without turbidity can be obtained. The polyaspartic acid ester (A1) is highly polar, so it is difficult to dissolve it in other resins or thickeners.

[0020] The proportion of the prepolymer (A2) in the solid content of the base may be 4% by mass or more and 50% by mass or less. When the proportion of the prepolymer (A2) is 4% by mass or more, color reversion can be further suppressed. When the proportion of the prepolymer (A2) is 50% by mass or less, the pot life can be longer. The proportion of the prepolymer (A2) may be 10% by mass or more, or may be 20% by mass or more. The proportion of the prepolymer (A2) may be 45% by mass or less, or may be 40% by mass or less.

[0021] (First polyaspartic acid ester (A21)) The first polyaspartic acid ester (A21) is a reaction product of a dialkyl ester (A21a) of a first dicarboxylic acid having 4 carbon atoms and a first polyamine (A21b).

[0022] The first polyamine (A21b) has two or more primary amino groups bonded to an alicyclic structure, and in the alicyclic structure, at least one of the carbon atoms adjacent to the carbon atoms to which each of the two or more primary amino groups is bonded has a hydrocarbon group as a substituent. In the first polyamine (A21b), the steric hindrance of the amino group that can be a reactive group with the curing agent (polyisocyanate compound (B1)) is large. The first polyamine (A21b) suppresses the reaction rate and contributes to extending the pot life.

[0023] The first polyaspartic acid ester (A21) may have an amine equivalent of 180 mgKOH / g or more and 210 mgKOH / g or less. The first polyaspartic acid ester (A21) may have an amine equivalent of 185 mgKOH / g or more and 190 mgKOH / g or more. The first polyaspartic acid ester (A21) may have an amine equivalent of 205 mgKOH / g or less and 200 mgKOH / g or less.

[0024] <Primary dicarboxylic acid dialkyl ester (A21a)> The dialkyl ester of the first dicarboxylic acid having 4 carbon atoms (A21a) is a dialkyl ester of maleic acid and / or fumaric acid, and is represented by the following general formula (I-1): [ka] (In the formula, R 11 and R 21 each independently represents an aliphatic hydrocarbon group having 1 to 20 carbon atoms. It is expressed as:

[0025] R 11 and R 21 R may be linear or branched. 11 and R 21 R does not have to have a ring structure. 11 and R 21 may be the same or different. 11 and R 21 may be the same.11 and R 21 The carbon number of R may be 1 to 10, or may be 2 to 4. 11 and R 21 may each be an ethyl group.

[0026] <First polyamine (A21b)> The first polyamine (A21b) has two or more primary amino groups bonded to an alicyclic structure, and in the alicyclic structure, at least one of the carbon atoms (β carbons) adjacent to the carbon atoms (α carbons) to which each of the two or more primary amino groups is bonded has a hydrocarbon group as a substituent.

[0027] The first polyamine (A21b) may be a diamine having two primary amino groups. The first polyamine (A21b) may be a diamine in which the two primary amino groups are bonded to different alicyclic structures.

[0028] The first polyamine (A21b) is, for example, a polyamine represented by the following general formula (II): [ka] (In the formula, R a1 , R a2 and R a3 each independently represents an aliphatic hydrocarbon group having 1 to 3 carbon atoms, α is the carbon atom to which the primary amino group is attached, and C β is C α ) It is expressed as:

[0029] R a1 and R a2 may be the same or different. a1 and R a2 may be the same. a1 and R a2 R may be a methyl group. a3 may be a methylene group.

[0030] Specific examples of the first polyamine (A21b) include 4,4'-diamino-3,3'-dimethyldicyclohexylmethane, 4,4'-diamino-3,3'-dipropyldicyclohexylpropane, 4,4'-diamino-3-ethyl-3'-propyldicyclohexylpropane, 4,4'-diamino-3,3'-diethyldicyclohexylpropane, and 4,4'-diamino-3,3'-dipropyldicyclohexylpropane.

[0031] The first polyaspartic acid ester (A21) is obtained by reacting one molecule of the first dicarboxylic acid dialkyl ester (A21a) with one primary amino group. The two or more first dicarboxylic acid dialkyl esters (A21a) reacting with the two or more primary amino groups may be the same or different. The two or more first dicarboxylic acid dialkyl esters (A21a) reacting with the two or more primary amino groups may be the same.

[0032] Specific examples of the first polyaspartic acid ester (A21) include those represented by the following general formula (a): [ka] (In the formula, R a1 , R a2 and R a3 is the same as in formula (II), and R 11 and R 21 has the same meaning as in general formula (I-1). It is expressed as:

[0033] Multiple R 11 may be the same or different. 11 may be the same. 21 may be the same or different. 21 may be the same for each.

[0034] Commercially available first polyaspartic acid esters (A21) include, for example, Desmophen NH1520 (manufactured by Covestro) and Feiaspartic F520 (manufactured by Feiyang).

[0035] (Second polyaspartic acid ester (A22)) The second polyaspartic acid ester (A22) is a reaction product of a dialkyl ester of a second dicarboxylic acid having 4 carbon atoms (A22a) and a second polyamine (A22b).

[0036] The second polyamine (A22b) is a polyamine other than the first polyamine (A21b), has two or more primary amino groups, and does not have an aromatic ring. In the second polyamine (A22b), the steric hindrance of the amino group that can be a reactive group with the curing agent (polyisocyanate compound (B1)) is relatively small. The second polyamine (A22b) increases the reaction rate and contributes to improving the drying property at room temperature.

[0037] The second polyaspartic acid ester (A22) may have an amine equivalent of 180 mgKOH / g or more and 210 mgKOH / g or less. The second polyaspartic acid ester (A22) may have an amine equivalent of 190 mgKOH / g or more and 200 mgKOH / g or more. The second polyaspartic acid ester (A22) may have an amine equivalent of 210 mgKOH / g or less and 205 mgKOH / g or less.

[0038] The first polyaspartic acid ester (A21) and the second polyaspartic acid ester (A22) may each have an amine equivalent of 180 mgKOH / g or more and 210 mgKOH / g or less.

[0039] <Secondary dicarboxylic acid dialkyl ester (A22a)> The dialkyl ester of the second dicarboxylic acid having 4 carbon atoms (A22a) is a dialkyl ester of maleic acid and / or fumaric acid represented by the following general formula (I-2): [ka] (In the formula, R 12 and R 22 each independently represents a chain aliphatic hydrocarbon group having 1 to 20 carbon atoms. It is expressed as:

[0040] R 12 and R 22 R may be linear or branched. 12 and R 22 R does not have to have a ring structure. 12 and R 22 may be the same or different. 12 and R 22 may be the same. 12 and R 22 The carbon number of R may be 1 to 10, or may be 2 to 4. 12 and R 22 may each be an ethyl group.

[0041] <Secondary polyamines (A22b)> The second polyamine (A22b) is other than the first polyamine (A21b) and has two or more primary amino groups but does not have an aromatic ring.

[0042] The second polyamine (A22b) may be a diamine having two primary amino groups. The second polyamine (A22b) may be a diamine having an aliphatic hydrocarbon group that does not have an alicyclic structure or an aromatic ring, and two primary amino groups. The second polyamine (A22b) may be a diamine having two or more primary amino groups bonded to an alicyclic structure, in which the β carbon does not have a hydrocarbon group as a substituent.

[0043] The second polyamine (A22b) is, for example, a polyamine represented by the following general formula (III): [ka] (In the formula, R a4 represents an aliphatic hydrocarbon group having 1 to 3 carbon atoms, Cα is the carbon atom to which the primary amino group is attached, and C β is C α ) It is expressed as:

[0044] R a4 may be a methylene group.

[0045] Specific examples of the second polyamine (A22b) include ethylenediamine, 1,2-diaminopropane, 1,4-diaminobutane, 1,3-diaminopentane, 1,5-diamino-2-methylpentane, 1,6-diaminohexane, 2,5-diamino-2,5-dimethylhexane, 2,2,4-trimethyl-1,6-diaminohexane, 2,4,4-trimethyl-1,6-diaminohexane, 1,11-diaminoundecane, 1,12-diaminododecane, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane (IPDA), and 4,4'-diaminodicyclohexylmethane. These may be used alone or in combination of two or more. The second polyamine (A22b) may be 4,4'-diaminodicyclohexylmethane.

[0046] The second polyaspartic acid ester (A22) is obtained by reacting one molecule of the second dicarboxylic acid dialkyl ester (A22a) with one primary amino group. The two or more second dicarboxylic acid dialkyl esters (A22a) reacting with the two or more primary amino groups may be the same or different. The two or more second dicarboxylic acid dialkyl esters (A22a) reacting with the two or more primary amino groups may be the same.

[0047] Specific examples of the second polyaspartic acid ester (A22) include those represented by the following general formula (b): [ka] (In the formula, R a4is the same as in formula (III), and R 12 and R 22 has the same meaning as in general formula (I-2). It is expressed as:

[0048] Multiple R 12 may be the same or different. 12 may be the same. 22 may be the same or different. 22 may be the same for each.

[0049] Commercially available second polyaspartic acid esters (A22) include, for example, Desmophen NH1220, Desmophen NH2885, Desmophen NH1420 (all manufactured by Covestro), Feiaspartic F220, and Feiaspartic F420 (all manufactured by Feiyang).

[0050] (Isocyanate compounds (A23)) The isocyanate compound (A23) is a difunctional or trifunctional isocyanate compound. Difunctional and trifunctional isocyanate compounds may be used in combination.

[0051] The isocyanate compound (A23) may be a primary isocyanate or a secondary isocyanate group. A primary isocyanate is an isocyanate having one carbon atom (-C-CH 2 Primary isocyanates are those with two carbon atoms bonded to a carbon atom having an isocyanate group (-C-CH(C)-N=C=O). Primary isocyanates can contribute to improving drying properties at room temperature. Secondary isocyanates are those with two carbon atoms bonded to a carbon atom having an isocyanate group bonded thereto (-C-CH(C)-N=C=O). Secondary isocyanates can contribute to extending the pot life.

[0052] The difunctional isocyanate compound (diisocyanate compound (A23a)) has two isocyanate groups in one molecule.

[0053] The diisocyanate compound (A23a) is represented by the following general formula (IV-1): [ka] (In the formula, Y 1 represents a hydrocarbon group. It is expressed as:

[0054] Examples of the diisocyanate compound (A23a) include aliphatic diisocyanates, alicyclic diisocyanates, araliphatic diisocyanates, and aromatic diisocyanates. These may be used alone or in combination of two or more.

[0055] Aliphatic diisocyanates do not have an aromatic ring and have two isocyanate groups bonded to carbon atoms constituting a linear or branched aliphatic hydrocarbon group. Examples of aliphatic diisocyanates include ethylene diisocyanate, trimethylene diisocyanate, 1,2-propylene diisocyanate, butylene diisocyanate (tetramethylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate), 1,5-pentamethylene diisocyanate (PDI), 1,6-hexamethylene diisocyanate (HDI), 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, heptamethylene diisocyanate, octamethylene diisocyanate, and dodecamethylene diisocyanate. These may be used alone or in combination of two or more.

[0056] Alicyclic diisocyanates do not have an aromatic ring, and have two isocyanate groups bonded to carbon atoms constituting a cyclic aliphatic hydrocarbon group. Examples of alicyclic diisocyanates include 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (common name: isophorone diisocyanate), methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane (common name: hydrogenated xylylene diisocyanate), and norbornane diisocyanate. These may be used alone or in combination of two or more.

[0057] Aromatic aliphatic diisocyanates have an aromatic ring and two isocyanate groups bonded to carbon atoms constituting an aliphatic hydrocarbon group. Examples of aromatic aliphatic diisocyanates include 1,3- or 1,4-xylylene diisocyanate, ω,ω'-diisocyanato-1,4-diethylbenzene, and 1,3- or 1,4-bis(1-isocyanato-1-methylethyl)benzene (common name: tetramethylxylylene diisocyanate). These may be used alone or in combination of two or more.

[0058] Aromatic diisocyanates have two isocyanate groups bonded to carbon atoms constituting an aromatic ring. Examples of aromatic diisocyanates include m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 2,4'- or 4,4'-diphenylmethane diisocyanate, 2,4- or 2,6-tolylene diisocyanate, 4,4'-toluidine diisocyanate, and 4,4'-diphenylether diisocyanate. These may be used alone or in combination of two or more.

[0059] The diisocyanate compound (A23a) may be an aliphatic diisocyanate or an alicyclic diisocyanate. The diisocyanate compound (A23a) may be at least one of hexamethylene diisocyanate and isophorone diisocyanate.

[0060] A trifunctional isocyanate compound (triisocyanate compound (A23b)) has three isocyanate groups in one molecule.

[0061] The triisocyanate compound (A23b) is represented by the following general formula (IV-2): [ka] (In the formula, Y 2 represents a hydrocarbon group. It is expressed as:

[0062] Examples of the triisocyanate compound (A23b) include aliphatic triisocyanates, alicyclic triisocyanates, araliphatic triisocyanates, and aromatic triisocyanates. These may be used alone or in combination of two or more.

[0063] Aliphatic triisocyanates do not have an aromatic ring and have three isocyanate groups bonded to carbon atoms constituting a linear or branched aliphatic hydrocarbon group. Examples of aliphatic triisocyanates include lysine ester triisocyanate, 1,4,8-triisocyanatooctane, 1,6,11-triisocyanatoundecane, 1,8-diisocyanato-4-isocyanatomethyloctane, 1,3,6-triisocyanatohexane, and 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyloctane. These may be used alone or in combination of two or more.

[0064] Alicyclic triisocyanates do not have an aromatic ring, and have three isocyanate groups bonded to carbon atoms constituting a cyclic aliphatic hydrocarbon group. Examples of alicyclic triisocyanates include 1,3,5-triisocyanatocyclohexane, 1,3,5-trimethylisocyanatocyclohexane, 2-(3-isocyanatopropyl)-2,5-di(isocyanatomethyl)-bicyclo[2.2.1]heptane, 2-(3-isocyanatopropyl)-2,6-di(isocyanatomethyl)-bicyclo[2.2.1]heptane, 3-(3-isocyanatopropyl)-2,5-di(isocyanatomethyl)-bicyclo[2.2.1]heptane, 5-(2-isocyanatoethyl)- Examples of such compounds include 2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo[2.2.1]heptane, 6-(2-isocyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo[2.2.1]heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo[2.2.1]heptane, and 6-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo[2.2.1]heptane. These compounds may be used alone or in combination of two or more.

[0065] Aromatic aliphatic triisocyanates have an aromatic ring and three isocyanate groups bonded to carbon atoms constituting an aliphatic hydrocarbon group. Examples of aromatic aliphatic triisocyanates include 1,3,5-triisocyanatomethylbenzene. These may be used alone or in combination of two or more.

[0066] Aromatic triisocyanates have three isocyanate groups bonded to carbon atoms constituting an aromatic ring. Examples of aromatic triisocyanates include triphenylmethane-4,4',4''-triisocyanate, 1,3,5-triisocyanatobenzene, and 2,4,6-triisocyanatotoluene. These may be used alone or in combination of two or more.

[0067] The triisocyanate compound (A23b) may be a trimer of the diisocyanate compound (A23a). The triisocyanate compound (A23b) may be a trimer of an aliphatic diisocyanate, or may be a trimer of hexamethylene diisocyanate. The trimer means a nurate, a biuret, or an adduct. The triisocyanate compound (A23b) may be at least one of a nurate, a biuret, and an adduct of hexamethylene diisocyanate.

[0068] The prepolymer (A2) is obtained by a Michael addition reaction of a first polyaspartic acid ester (A21), a second polyaspartic acid ester (A22), and a difunctional or trifunctional isocyanate compound (A23).

[0069] The sum of the first and second diaspartic acid esters (A21, A22) and the diisocyanate compound (A23a) is, for example, the total amine equivalent (NH 2 ) / isocyanate equivalent (NCO) is 12 / 6 to 8 / 6. 2 The / NCO may be from 10 / 6 to 8 / 6, and may be 9 / 6.

[0070] The total of the first and second diaspartic acid esters (A21, A22) and the triisocyanate compound (A23b) are reacted, for example, such that the total amine equivalent / isocyanate equivalent is 2 / 1.

[0071] The ratio (m1:m2) of the number of moles m1 of the first polyaspartic acid ester (A21) to the number of moles m2 of the second polyaspartic acid ester (A22) used in the synthesis of the prepolymer (A2) is 1:1 to 4:1.

[0072] This allows a greater number of residues of the first polyaspartic acid ester (A21) than the second polyaspartic acid ester (A22) to be introduced into the prepolymer (A2), thereby controlling the curability of the clear coating composition. As a result, a long pot life and room temperature drying properties are both achieved. If the number of moles of the first polyaspartic acid ester (A21) used in the synthesis of the prepolymer (A2) is small, the pot life becomes short. If the number of moles of the second polyaspartic acid ester (A22) is small, the room temperature drying properties decrease.

[0073] The ratio (m1:m2) may be from 1:1 to 3:1, or may be from 3:2 to 7:3.

[0074] The prepolymer (A2) can be obtained, for example, by multi-stage synthesis. The prepolymer (A2) can be obtained, for example, by reacting an isocyanate compound (A23) with a predetermined amount of a first polyaspartic acid ester (A21) and then reacting the second polyaspartic acid ester (A22). According to this method, the residue of the first polyaspartic acid ester (A21) can be introduced into the prepolymer (A2) in a desired ratio.

[0075] The prepolymer (A2) may contain a reaction product of the first and second diaspartic acid esters (A21, A21) with a diisocyanate compound (A23a) and a reaction product of the first and second diaspartic acid esters (A21, A21) with a triisocyanate compound (A23b). This makes it possible to easily adjust the number of residues of the first polyaspartic acid ester (A21) and the number of residues of the second polyaspartic acid ester (A22) in the entire prepolymer (A2) to a desired ratio.

[0076] The first dicarboxylic acid dialkyl ester (A21a) and the second dicarboxylic acid dialkyl ester (A22a), which are the raw materials of the prepolymer (A2), may be the same or different. The first dicarboxylic acid dialkyl ester (A21a) and the second dicarboxylic acid dialkyl ester (A22a) may be the same.

[0077] The prepolymer (A2) may have a molecular weight of 1,000 or more and 100,000 or less. The prepolymer (A2) may have a molecular weight of 1,500 or more. The prepolymer (A2) may have a molecular weight of 50,000 or less, or 10,000 or less.

[0078] The prepolymer (A2a) which is a reaction product of the first polyaspartic acid ester (A21) and the second polyaspartic acid ester (A22) in a ratio (m1:m2) of 1:1 with the diisocyanate compound (A23a) can be represented, for example, by the following general formula: [ka] (In the formula, X 1 represents a group other than the amino group of the first polyamine, and X 2 represents a group other than the amino group of the second polyamine, and X 3 represents a group other than an amino group of the first or second polyamine, R 13 is R 11 or R 12 and R 23 is R 21 or R 22 and Y 1 has the same meaning as in formula (IV-1) and represents a group other than the isocyanate group of the isocyanate compound (A23), and n is 1 to 3. It is expressed as:

[0079] The polyamine contained in the repeating unit may be either the first polyamine or the second polyamine since it is not involved in the reaction with the polyisocyanate compound (B1). The prepolymer (A2a) may have the same number of residues of the first polyaspartic acid ester (A21) as the number of residues of the second polyaspartic acid ester (A22).

[0080] The prepolymer (A2b) which is a reaction product of the first polyaspartic acid ester (A21) and the second polyaspartic acid ester (A22) in a ratio (m1:m2) of 2:1 with the triisocyanate compound (A23b) can be represented, for example, by the following general formula: [ka] (In the formula, X 1 represents the residue of a first polyamine, and X 2 represents the residue of a second polyamine, Y 2 has the same meaning as in formula (IV-2) and represents a group other than the isocyanate group of the isocyanate compound (A23). It is expressed as:

[0081] The prepolymer (A2b) has a greater number of residues of the first polyaspartic acid ester (A21) than of the second polyaspartic acid ester (A22).

[0082] The prepolymers (A2a, A2b) are examples of reaction products of the first polyaspartic acid ester (A21) and the second polyaspartic acid ester (A22) with the di- or triisocyanate compound (A23a, A23b).

[0083] Polyaspartic acid ester (A1) The polyaspartic acid ester (A1) is, for example, a reaction product between a dialkyl ester of a dicarboxylic acid having 4 carbon atoms (a tertiary dicarboxylic acid dialkyl ester) and a polyamine (a tertiary polyamine).

[0084] The third dicarboxylic acid dialkyl ester may be the same as the first dicarboxylic acid dialkyl ester (A21a) or the second dicarboxylic acid dialkyl ester (A22a) described above.

[0085] The third polyamine may be the same as the first polyamine (A21b) or the second polyamine (A22b). The third polyamine may be the same as the second polyamine (A22b). The third polyamine may be a diamine having two or more primary amino groups bonded to an alicyclic structure, in which the β carbon of the alicyclic structure does not have a hydrocarbon group as a substituent. The third polyamine may be a diamine represented by the general formula (III) above.

[0086] The polyaspartic acid ester (A1) may have a structure similar to that exemplified as the first polyaspartic acid ester (A21), or may have a structure similar to that exemplified as the second polyaspartic acid ester (A22). The polyaspartic acid ester (A1) may have a structure similar to that exemplified as the second polyaspartic acid ester (A22).

[0087] The proportion of the polyaspartic acid ester (A1) in the solid content of the base material may be 43% by mass or more and 89% by mass or less. The proportion of the polyaspartic acid ester (A1) may be 50% by mass or more, or 60% by mass or more. The proportion of the polyaspartic acid ester (A1) may be 80% by mass or less.

[0088] Organic solvents The base agent may contain an organic solvent. Examples of the organic solvent include ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol divinyl ether, diethylene glycol ethyl methyl ether, diethylene glycol isopropyl methyl ether, diethylene glycol butyl methyl ether, triethylene glycol dimethyl ether, triethylene glycol divinyl ether, tetraethylene glycol diethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol di-n-propyl ether, propylene glycol diisopropyl ether, propylene glycol di-n-butyl ether, propylene glycol diisobutyl ether, propylene glycol diallyl ether, propylene glycol diphenyl ether, dipropylene glycol dimethyl ether (DPDM), dipropylene glycol diethyl ether, dipropylene glycol di-n-butyl ether, dipropylene glycol diiso ... glycol ether-based organic solvents such as pyrene glycol diallyl ether, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, tripropylene glycol di-n-butyl ether, tripropylene glycol diisobutyl ether, tripropylene glycol diallyl ether, butylene glycol dimethyl ether, butylene glycol diethyl ether, butylene glycol di-n-butyl ether, 2-butoxyethyl diethoxyethyl ether, 2-butoxyethyl triethoxy ether, and 2-butoxyethyl tetraethoxyethyl ether; acetate-based organic solvents such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol mono-n-butyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol mono-n-butyl ether acetate, 3-methoxybutyl acetate, and propylene glycol monomethyl ether acetate; ketone-based organic solvents such as acetone, methyl ethyl ketone, methyl amyl ketone, and methyl isobutyl ketone;Ester-based organic solvents such as ethyl acetate, butyl acetate, isobutyl acetate, methyl benzoate, ethyl ethoxypropionate, ethyl propionate, and methyl propionate; These may be used alone or in combination of two or more.

[0089] Other film-forming resins The base material may contain other film-forming resins. Examples of the film-forming resins include acrylic resins, polyester resins, polyurethane resins, and silicone acrylic resins. From the viewpoint of compatibility, the content of the other film-forming resins may be, for example, 10% by mass or less, 5% by mass or less, or 2% by mass or less of the solid content of the base material.

[0090] Additives The base material may contain various additives. Examples of additives include dispersants, defoamers, ultraviolet absorbers, hindered amine light stabilizers, antioxidants, viscosity regulators, surface conditioners, film-forming assistants, rust inhibitors, and thickeners. From the viewpoint of compatibility, the content of the additives may be, for example, 15% by mass or less, 10% by mass or less, or 8% by mass or less of the solid content of the base material.

[0091] -How to prepare the base agent The base material is prepared by mixing the above-mentioned components by a method known to those skilled in the art, for example, using a commonly used mixing device such as a paint shaker or mixer.

[0092] <Hardening agent> The curing agent contains a polyisocyanate compound (B1). The solid content concentration of the curing agent is, for example, 50% by mass or more and 90% by mass or less. The solid content concentration of the curing agent may be 70% by mass or less.

[0093] The polyisocyanate compound (B1) is not particularly limited as long as it has two or more isocyanate groups on average in one molecule. For example, the polyisocyanate compound (B1) may be at least one of the diisocyanate compound (A23a) and the triisocyanate compound (A23b) described above. The polyisocyanate compound (B1) may be a tetrafunctional or higher isocyanate compound such as 4,4'-diphenylmethane-2,2',5,5'-tetraisocyanate.

[0094] The polyisocyanate compound (B1) may be a derivative of the above di- or triisocyanate compound, such as a dimer, trimer, biuret, allophanate, uretdione, uretoimine, isocyanurate, oxadiazinetrione, polymethylene polyphenyl polyisocyanate (crude MDI, polymeric MDI), or crude TDI.

[0095] Organic solvents The curing agent may contain an organic solvent. Examples of the organic solvent include the same organic solvents as those exemplified as those that may be contained in the base agent.

[0096] Other hardening ingredients The curing agent may contain a curing component other than the polyisocyanate compound (B1). The curing component other than the polyisocyanate compound (B1) may be, for example, a silane coupling agent. The content of the other curing component may be, for example, 10% by mass or less of the total solid content of all the curing components.

[0097] Additives The curing agent may contain various additives. The additives may be the same as those listed as those that may be contained in the base agent. The content of the additives may be, for example, 5% by mass or less, 2% by mass or less, or 0.5% by mass or less of the solid content of the curing agent.

[0098] - Preparation method of hardener The hardener is prepared by mixing the above components in the manner described above.

[0099] Method for preparing multi-liquid clear coating composition The multi-liquid clear coating composition is prepared by mixing the base agent and the curing agent, and, if necessary, diluting components, etc., by the above-mentioned method. The base agent and the curing agent are usually mixed immediately before use (for example, the composition is used within 60 minutes after mixing the respective agents).

[0100] As the diluting component, the organic solvents exemplified as those that can be contained in the base agent can be exemplified. The multi-liquid clear coating composition according to the present disclosure is a solvent-based composition.

[0101] The base agent and the curing agent are such that the total amine equivalent of the polyaspartic acid ester (A1) and the prepolymer (A2) of the polyaspartic acid ester and the isocyanate group equivalent of the polyisocyanate compound (B1) are in the range of amine equivalent (NH 2 ) / isocyanate group equivalent (NCO) = 1 / 0.5 to 1 / 1.5.

[0102] [Multi-layer coating] The multilayer coating film according to the present disclosure comprises a colored base coating film disposed on a substrate, and a clear coating film disposed on the colored base coating film and formed from the above multi-liquid clear coating composition. The multilayer coating film according to the present disclosure is suppressed from returning to its original color and has excellent design.

[0103] <Object to be coated> The shape of the substrate is not particularly limited. The substrate may be flat or three-dimensional. The material of the substrate is not particularly limited. Examples of the material of the substrate include metal, resin, and glass. Examples of metal include iron, copper, aluminum, tin, zinc, and alloys thereof.

[0104] The metal substrate may be surface-treated. Examples of the surface treatment include phosphate treatment, chromate treatment, zirconium conversion treatment, and composite oxide treatment. The metal substrate may be further coated with an electrodeposition paint after the surface treatment. The electrodeposition paint may be of the cationic type or the anionic type.

[0105] Examples of the resin include polypropylene resin, polycarbonate resin, urethane resin, polyester resin, polystyrene resin, ABS resin, vinyl chloride resin, and polyamide resin. The resin substrate may be degreased.

[0106] Specific examples of the substrate include automobile bodies such as passenger cars, trucks, motorcycles, and buses, or parts thereof.

[0107] The substrate may be coated with one or more layers of primer paint and / or undercoat paint for repair (also called primer surfacer). Primer paint and undercoat paint for repair may be, for example, a water-based or solvent-based two-component urethane paint.

[0108] <Colored base coating> The colored base coating film is formed from a colored base paint composition. The thickness of the colored base coating film is, for example, 10 μm or more and 100 μm or less.

[0109] The colored base coating composition may be of a curing type or a lacquer type. The curing type colored base coating composition contains a curable resin (e.g., a hydroxyl group-containing resin) and a curing agent (e.g., a polyisocyanate compound), and a cured coating film is formed by heating. The lacquer type colored base coating composition contains water and / or an organic solvent and a binder resin dissolved or dispersed therein, and a cured coating film is formed by volatilization of the water and / or organic solvent. Examples of binder resins include acrylic resins, amino alkyd resins, alkyd resins, amino resins, isocyanate resins, epoxy resins, vinyl chloride resins, cashew resins, silicone resins, styrene resins, styrenated alkyd resins, cellulose-based resins (e.g., cellulose nitrate, etc.), urea resins, vinyl resins, phenolic resins, phthalic acid resins, fluororesins, polyester resins, unsaturated polyester resins, and modified resins thereof (e.g., rosin-modified, phenol-modified, epoxy resin-modified, styrene-modified, acrylic-modified, urethane-modified). These may be used alone or in combination of two or more. Examples of the organic solvent include naphtha, xylene, toluene, and acetone.

[0110] The colored base coating composition contains a pigment. Examples of the pigment include color pigments and / or luster pigments. Examples of the color pigment include titanium dioxide, carbon black, iron oxide, and copper phthalocyanine blue. Examples of the luster pigment include aluminum flakes and mica flakes.

[0111] <Clear coating> The clear coating film is formed from the above-mentioned multi-liquid clear coating composition. The thickness of the clear coating film is, for example, 20 μm or more and 100 μm or less.

[0112] [Method of forming multi-layer coating film] The method for forming a multilayer coating film according to the present disclosure comprises applying a colored base coating composition onto a substrate to form a colored base coating film, and applying the above-mentioned multi-component clear coating composition onto the colored base coating film to form a clear coating film.

[0113] (1) The process of forming a colored base coating In this step, the colored base coating composition is applied onto the substrate to form a colored base coating film. The colored base coating composition may be applied multiple times. Examples of the application method include air spray coating, airless spray coating, rotary atomization coating, and curtain coat coating. These methods may be combined with electrostatic coating. In the case of repair, air spray coating may be used because it is easy to apply localized coating. The application may be applied multiple times. After application, the coating film is cured. The curing conditions are appropriately set depending on the composition of the colored base coating composition.

[0114] (2) Process for forming a clear coating In this step, a multi-liquid clear coating composition is applied onto the colored base coating film to form a clear coating film. The coating method is not particularly limited, and may be the same as that for the colored base coating composition. The application of the multi-liquid clear coating composition may be performed multiple times. The coating film is then cured (dried). The coating film may be forced dried, may be dried at room temperature, or may be a combination of these. In the forced drying, the coating is heated, for example, at 40°C or higher and 100°C or lower for about 5 to 60 minutes. In the room temperature drying, the coating is dried at room temperature (15°C or higher and 25°C or lower), for example, for 1 to 5 hours. EXAMPLES

[0115] Hereinafter, the present embodiment will be described in more detail using examples, but the present embodiment is not limited by the examples. In the examples, "parts" and "%" are based on mass unless otherwise specified.

[0116] The following were used as each component. Polyaspartic acid ester (A1) Trade name: Desmophen NH1420, manufactured by Covestro, amine equivalent 201 mg KOH / g, represented by the above general formula (b), R a4 is a methylene group, and R 12 and R 22 are all ethyl groups. · Primary polyaspartic acid ester (A21) Trade name: Desmophen NH1520, manufactured by Covestro, amine equivalent: 192 mg KOH / g, represented by the above general formula (a), R a1 and R a2 are both methyl groups, and R a3 is a methylene group, and R 11 and R 21 are all ethyl groups. Secondary polyaspartic acid ester (A22) Product name: Desmophen NH1420 ·Diisocyanate compounds (A23a) Product name: HDI, Tosoh Corporation, 1,6-hexamethylene diisocyanate ·Triisocyanate compounds (A23b) Product name: Desmodur N 3900, manufactured by Covestro, 1,6-hexamethylene diisocyanate nurate Polyisocyanate compounds (B1) (B1-1) Product name: Desmodur N 3900, manufactured by Covestro, nurate form of 1,6-hexamethylene diisocyanate (B1-2) Product name: Desmodur N Z4470BA, manufactured by Covestro, nurate form of isophorone diisocyanate

[0117] [Example 1] A multi-liquid type clear coating composition was prepared and a coated article was produced as follows. (1) Preparation of multi-liquid clear coating composition (1-1) Synthesis of prepolymer The first polyaspartic acid ester (A21) and the triisocyanate compound (A23b) were reacted at 85°C for 6 hours. Next, the second polyaspartic acid ester (A22) was added so that the molar ratio with the first polyaspartic acid ester (A21) was 1:1, and the reaction was carried out at 85°C for 5 hours to synthesize the prepolymer (A2b). All reactions were carried out with stirring, and triethylamine was added as a catalyst at 0.05% relative to the solid content of the prepolymer (A2b). The molecular weight of the prepolymer (A2b) was 2500. The molecular weight was the weight average molecular weight determined by GPC, and TSKgel guardcolumn SuperAW-H and TSKgel Super AWM-H were used as columns.

[0118] (1-2) Preparation of base agent The polyaspartic acid ester (A1), the prepolymer (A2b), and an organic solvent (butyl acetate) were mixed to prepare a base material. The proportion of the polyaspartic acid ester (A1) in the solid content of the base material was 73%, and the proportion of the prepolymer (A2) in the solid content of the base material was 20%.

[0119] (1-3) Mixing the base agent and hardener A curing agent was prepared by mixing a total of 65 parts of the polyisocyanate compound (B1-1) and polyisocyanate (B1-2) and 18 parts of an organic solvent (butyl acetate). The base agent, hardener, and diluent (butyl acetate) are mixed in a total amine equivalent (NH 2 A multi-liquid clear coating composition (solids concentration 50%) was prepared by mixing them so that the ratio of the isocyanate group equivalent (NCO) to the isocyanate group equivalent (NCO) was 91 / 100.

[0120] (2) Preparation of painted items (2-1) Formation of base coating A primer surfacer was prepared by mixing 100 parts of nax Urethane Primer Surface Pro V1 Gray (main agent, manufactured by Nippon Paint), 20 parts of nax Urethane Primer Surface Pro V1 Hardener (hardener, manufactured by Nippon Paint), and an appropriate amount of nax Multi-Urethane Thinner (diluting component, manufactured by Nippon Paint).

[0121] A primer surfacer was applied to a 60 cm x 40 cm steel plate (substrate) using a spray gun, and the plate was air-blow dried until the paint no longer adhered to the surface when touched with a finger. This application and drying process was repeated two more times. The steel plate was then placed in an oven set at 60°C and heated for 30 minutes to form a cured coating film. The surface of the resulting coating film was then polished. Finally, the surface of the coating film was degreased to prepare a substrate with a base coating film (cured film thickness 45 μm).

[0122] (2-2) Formation of colored base coating A lacquer-type colored base coating composition was prepared by mixing 100 parts of nax Real 1G3 Gray Metallic (manufactured by Nippon Paint Co., Ltd.) and 40 parts of nax Stabi R NEO (dilution component, manufactured by Nippon Paint Co., Ltd.).

[0123] The colored base coating composition was applied to a substrate having a base coating film using a spray gun, and the substrate was dried with an air blower until the coating no longer adhered to the substrate when touched with a finger. This coating and drying process was repeated two more times to form a colored base coating film (cured film thickness: 20 μm).

[0124] (2-3) Formation of clear coating A multi-liquid clear coating composition was applied twice onto the colored base coating film using a spray gun. Each application was performed with an interval of 1 minute. In this way, an uncured clear coating film was formed. Thereafter, the coated object with the uncured clear coating film was left to stand for 15 minutes in an environment with a temperature of 23±2°C and a humidity of 50±2 RH%. In this way, a coated article with a multi-layer coating film was produced.

[0125] [Examples 2 to 11, Comparative Example 5] A prepolymer and a multi-liquid clear coating composition were prepared and a coated article was produced in the same manner as in Example 1, except that the components and amounts used were changed as shown in Table 1.

[0126] [Evaluation method] The multi-liquid clear coating composition and the multi-layer coating film were evaluated by the following methods. The evaluation results are shown in Table 1.

[0127] The contents (%) of (A2a) prepolymer and (A2b) prepolymer in Table 1 indicate the proportions of each prepolymer in the solid content of the base resin.

[0128] (1) Color reversion - Preparation of standard multi-layer coating First, a multi-layer coating film to be used as the evaluation standard was prepared in the same manner as in Example 1, except that Nax Aegis (3:1) RS Clear (manufactured by Nippon Paint Co., Ltd.) was used as the clear coating composition.

[0129] The value E is measured by a spectrophotometer using a light source that is incident on the surface of the clear coating at a 45 degree angle and reflected at a 15 degree angle to the regular reflected light. 0 The difference (color difference ΔE) between the value E(15°) of the multilayer coating film obtained in the examples or comparative examples and the value E(15°) of the multilayer coating film obtained in the examples or comparative examples was calculated. The smaller the color difference ΔE, the better the resistance to color reversion, and ΔE<5 can be said to be suitable for practical use.

[0130] (2) Pot life The base resin, hardener and diluent were each placed at 20°C to keep the liquid temperature constant. Then, a predetermined amount of each liquid was mixed in order to prepare a multi-liquid clear coating composition. Immediately, a viscosity cup NK-2 manufactured by Anest Iwata Corporation was immersed in this multi-liquid clear coating composition and then pulled up. The time from the moment of pulling up until all of the multi-liquid clear coating composition was discharged was measured. This was called the initial value T 0 (seconds).

[0131] Next, after preparing the multi-liquid clear coating composition, it was left to stand for 45 minutes, and the time (T (seconds)) from when it was pulled up to when it was discharged was measured in the same manner as above. 0 (Seconds) was calculated. TT 0 If (seconds)≦5, it can be said to be suitable for practical use.

[0132] (Evaluation Criteria) A:TT 0 ≦5 (seconds) B:5 (seconds) <T-T 0 ≦20(seconds) C:TT 0 >20(seconds)

[0133] (3) Drying at room temperature A multi-liquid clear coating composition was spray-coated on the colored base coating film prepared in the same manner as above, and the composition was left to cure for 60 minutes under conditions of 23°C and 50% RH to prepare a test panel. A finger touch test was carried out on the obtained test panel, and the panel was evaluated according to the following criteria. A rating of B or higher can be said to be suitable for practical use. In the case of a rating of A, polishing work is possible one hour after painting.

[0134] (Evaluation Criteria) A: Even if I touched it hard, my finger marks did not remain on the coating. B: When lightly touched, no finger marks were left on the coating film. C: Finger marks remain on the coating even when touched lightly.

[0135] [Table 1]

[0136] As can be seen from Table 1, the clear coating compositions of the examples had a sufficiently long pot life and excellent drying properties at room temperature. In the multilayer coating films obtained from these compositions, color reversion was also suppressed. The clear coating compositions of Examples 2, 3, 6-8, and 10-11 were particularly excellent in terms of the balance between the long pot life, drying properties at room temperature, and resistance to color reversion.

[0137] In Comparative Example 1, the prepolymer was synthesized only from the low-reactivity first polyamine (A21b), so the clear coating composition after application had a low viscosity and color reversion occurred. In Comparative Example 2, the prepolymer was synthesized only from the highly reactive second polyamine (A22b), so the pot life was short. In Comparative Example 3, the prepolymer (A2) was not used, so the color reversion resistance was poor. In Comparative Example 4, the curing agent was not used, so the room temperature drying property was reduced and the color reversion resistance was also poor. In Comparative Example 5, the polyaspartic acid ester (A1) was not used, so the room temperature drying property was reduced and the color reversion resistance was also poor.

[0138] The present invention includes the following aspects. [1] A base material including a polyaspartic acid ester (A1) and a prepolymer of the polyaspartic acid ester (A2); A curing agent containing a polyisocyanate compound (B1), The prepolymer (A2) is a reaction product obtained by reacting a first polyaspartic acid ester (A21) and a second polyaspartic acid ester (A22) with a difunctional or trifunctional isocyanate compound (A23) such that the ratio (m1:m2) of the number of moles m1 of the first polyaspartic acid ester (A21) to the number of moles m2 of the second polyaspartic acid ester (A22) is 1:1 to 4:1; The first polyaspartic acid ester (A21) is a dialkyl ester of a first dicarboxylic acid having four carbon atoms (A21a); a first polyamine (A21b) having two or more primary amino groups bonded to an alicyclic structure, in which at least one of the carbon atoms adjacent to the carbon atoms to which each of the two or more primary amino groups is bonded has a hydrocarbon group as a substituent; The second polyaspartic acid ester (A22) is a dialkyl ester of a second dicarboxylic acid having four carbon atoms (A22a); and a second polyamine (A22b) other than the first polyamine (A21b), which has two or more primary amino groups and has no aromatic ring, said second polyamine (A22b) being a reaction product thereof. [2] The dialkyl ester of the first dicarboxylic acid (A21a) and the dialkyl ester of the second dicarboxylic acid (A22a) are each independently represented by the following general formula (I): [ka] (In the formula, R 1 and R 2 each independently represents a chain aliphatic hydrocarbon group having 1 to 20 carbon atoms.) The multi-component clear coating composition according to the above [1], [3] The first polyamine (A21b) is represented by the following general formula (II): [ka] (In the formula, R a1 , R a2 and R a3 each independently represents an aliphatic hydrocarbon group having 1 to 3 carbon atoms, α is the carbon atom to which the primary amino group is attached, and C β is C α ) The multi-component clear coating composition according to the above [1] or [2], [4] The second polyamine (A22b) has the following general formula (III): [ka] (In the formula, R a4 represents an aliphatic hydrocarbon group having 1 to 3 carbon atoms, C α is the carbon atom to which the primary amino group is attached, and C β is C α ) The multi-component clear coating composition according to any one of the above [1] to [3], [5] The prepolymer (A2) may have a molecular weight of 1,000 or more and 100,000 or less, as in any one of the above multi-liquid clear coating compositions [1] to [4]. [6] The multi-component clear coating composition according to any one of the above [1] to [5], wherein the first polyaspartic acid ester (A21) and the second polyaspartic acid ester (A22) each have an amine equivalent of 180 mgKOH / g or more and 210 mgKOH / g or less. [7] The multi-liquid clear coating composition according to any one of the above [1] to [6], wherein the proportion of the prepolymer (A2) in the solid content of the main component is from 4 mass % to 50 mass %. [8] the bifunctional isocyanate compound (A23) is at least one of 1,6-hexamethylene diisocyanate and isophorone diisocyanate, The multi-liquid clear coating composition according to any one of the above [1] to [7], wherein the trifunctional isocyanate compound (A23) is at least one of a nurate form, a biuret form and an adduct form of 1,6-hexamethylene diisocyanate. [9] A colored base coating film disposed on an object to be coated; A multi-layer coating film comprising: a clear coating film disposed on the colored base coating film and formed from any one of the multi-component clear coating compositions [1] to [8] above.

[10] Applying a colored base coating composition onto an object to form a colored base coating film; A method for forming a multilayer coating film, comprising: coating the multi-component clear coating composition of any one of [1] to [8] above on the colored base coating film to form a clear coating film. [Industrial Applicability]

[0139] According to the present invention, there is provided a multi-liquid clear coating composition having excellent resistance to color reversion, as well as room temperature drying properties and a long pot life. Therefore, the multi-liquid clear coating composition is particularly suitable for forming a clear coating film for automobile repair.

Claims

1. A base material including a polyaspartic acid ester (A1) and a prepolymer of the polyaspartic acid ester (A2); A curing agent containing a polyisocyanate compound (B1), The prepolymer (A2) is a reaction product obtained by reacting a first polyaspartic acid ester (A21) and a second polyaspartic acid ester (A22) with a bifunctional or trifunctional isocyanate compound (A23) such that the ratio (m1:m2) of the number of moles m1 of the first polyaspartic acid ester (A21) to the number of moles m2 of the second polyaspartic acid ester (A22) is 1:1 to 4:1; The first polyaspartic acid ester (A21) is A dialkyl ester of a first dicarboxylic acid having 4 carbon atoms (A21a), and a first polyamine (A21b) having two or more primary amino groups bonded to an alicyclic structure, in which at least one of the carbon atoms adjacent to the carbon atoms to which each of the two or more primary amino groups is bonded has a hydrocarbon group as a substituent, The second polyaspartic acid ester (A22) is A dialkyl ester of a secondary dicarboxylic acid having 4 carbon atoms (A22a), and a second polyamine (A22b) other than the first polyamine (A21b), which has two or more primary amino groups and has no aromatic ring.

2. The dialkyl ester of the first dicarboxylic acid (A21a) and the dialkyl ester of the second dicarboxylic acid (A22a) are each independently represented by the following general formula (I): 【Chemistry 1】 (In the formula, R １ and R ２ each independently represents a chain aliphatic hydrocarbon group having 1 to 20 carbon atoms. The multi-liquid clear coating composition according to claim 1, wherein the multi-liquid clear coating composition is represented by the formula:

3. The first polyamine (A21b) is represented by the following general formula (II): 【Chemistry 2】 (In the formula, R ａ１ , R ａ２ and R ａ３ each independently represents an aliphatic hydrocarbon group having 1 to 3 carbon atoms; α is the carbon atom to which a primary amino group is attached, and C β is C α ) 3. The multi-liquid clear coating composition according to claim 1 or 2, wherein the multi-liquid clear coating composition is represented by the formula:

4. The second polyamine (A22b) has the following general formula (III): 【Chemistry 3】 (In the formula, R ａ４ represents an aliphatic hydrocarbon group having 1 to 3 carbon atoms, C α is the carbon atom to which a primary amino group is attached, and C β is C α ) 3. The multi-liquid clear coating composition according to claim 1 or 2, wherein the multi-liquid clear coating composition is represented by the formula:

5. 3. The multi-component clear coating composition according to claim 1, wherein the prepolymer (A2) has a molecular weight of 1,000 or more and 100,000 or less.

6. The multi-component clear coating composition according to claim 1 or 2, wherein the first polyaspartic acid ester (A21) and the second polyaspartic acid ester (A22) each have an amine equivalent of 180 mg KOH / g or more and 210 mg KOH / g or less.

7. 3. The multi-component clear coating composition according to claim 1, wherein the proportion of said prepolymer (A2) in the solid content of said base resin is 4 mass % or more and 50 mass % or less.

8. The bifunctional isocyanate compound (A23) is at least one of 1,6-hexamethylene diisocyanate and isophorone diisocyanate, 3. The multi-liquid clear coating composition according to claim 1, wherein the trifunctional isocyanate compound (A23) is at least one of a nurate, a biuret and an adduct of 1,6-hexamethylene diisocyanate.

9. A colored base coating film disposed on an object to be coated; A multi-layer coating film comprising: a clear coating film disposed on the colored base coating film and formed from the multi-liquid clear coating composition according to claim 1 or 2.

10. Applying a colored base coating composition onto an object to form a colored base coating film; A method for forming a multi-layer coating film, comprising: coating the multi-component clear coating composition according to claim 1 or 2 on the colored base coating film to form a clear coating film.

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